1. Field of the Invention
The invention relates to the removal of contaminants from a hydraulic system.
2. Description of the Prior Art
The braking system of a motor vehicle is generally bled by opening the bleed valve for each brake individually and pumping the brakes. This procedure not only requires two people but is also very time-consuming.
These drawbacks are overcome by U.S. Pat. No. 4,038,823 in which a reciprocating pump is used to pump brake fluid into the servo cylinders of the braking system. Bleeding of a brake is complete when clear brake fluid enters the reservoir of the master cylinder. In order for the person bleeding the brakes to ascertain that clear brake fluid is entering the reservoir, a long feed line must be provided from the pump to the brake being bled. This is cumbersome.
U.S. Pat. No. 4,741,417 employs a motor-driven rotary pump for bleeding a braking system. The pump inlet is immersed in the reservoir of the master cylinder while the pump outlet is connected to a manifold. Flexible hoses lead from the manifold to the bleed valves of the respective servo cylinders. In operation, brake fluid is pumped from the reservoir to the servo cylinders via the manifold and the flexible hoses. The brake fluid returns to the reservoir through the brake lines of the braking system. This arrangement is complicated and, in addition, requires considerable time to set up.
U.S. Pat. No. 4,785,629 eliminates these problems by injecting brake fluid into the servo cylinders via a syringe. However, the syringe is associated with its own difficulties. To begin with, two hands are required to operate the syringe. Furthermore, the syringe cannot be very large since otherwise the force necessary to operate the syringe becomes excessive. Due to the limited size of the syringe, the syringe must be refilled frequently thereby increasing the time to bleed the braking system. In addition, the refilling operation requires disconnection of the syringe from the brake system and the attendant risk of introducing air upon reconnection. Moreover, following the injection of brake fluid with the syringe, the master cylinder must be observed to insure that all air bubbles are dissipated. Finally, as a practical matter people tend to impart too much force to the syringe at the beginning of each bleeding operation and cause rapid flow and upward splashing and/or spilling of fluid from the master cylinder.
Prior application Ser. No. 08/441,187 discloses a portable pump or fluid conveying device which is simpler and quicker than the syringe. Although the pump operates very satisfactorily, it has been found that certain improvements would be beneficial. For instance, the prior application fails to teach a convenient manner of priming the pump. Moreover, while the prior application discloses pressure bleeding, there are situations where vacuum bleeding, either alone or in combination with pressure bleeding, yields best results. Accordingly, it would be of advantage if the pump could be easily switched back-and-forth. Furthermore, although the prior application shows the pump connected to the servo cylinder of a brake system, pressure bleeding through a master cylinder reservoir is recommended under certain circumstances. However, since different reservoirs have openings of different size, it is not possible to employ the pump for a variety of reservoirs.
In addition, a problem exists with the portable pump as well as with other arrangements for bleeding or flushing hydraulic systems. This is the lack of any provision for protecting hydraulic fluid from air when hydraulic fluid is delivered to a hydraulic system. Thus, hydraulic fluid tends to deteriorate when it comes into contact with air. The improvements addressed in this application are directed at solving these problems.